TESTS OF A BABCOCK & WILCOX BOILER BUILT FOR

THE U. S. S. "CINCINNATI":

In the annual report of the Chief of the Bureau of Steam Engineering there is published a report of tests made on one of eight new boilers built by The Babcock & Wilcox Company for the "Cincinnati," by a board composed of Lieutenant-Commander A. B. Willits and Lieutenant B. C. Bryan, U. S. N. These tests were made June 15 to 22, 1900, at the works of the builders, Elizabethport, N. J., and the following synopsis includes all but the detailed tabulations from which the important data given was deduced."

DESCRIPTION OF BOILER AND APPURTENANCES

The boiler is of the Babcock & Wilcox new marine type, composed entirely of wrought steel, the point of difference between it and the older type of this make of boiler being in the arrangement of baffle plates (as shown in the sectional view on the following page) which compel the products of combustion to pass three times across the tubes before entering the up-take. The small tubes are 2 inches outside diameter, while the bottom tube in each section or element, is 4 inches outside diameter. The total heating surface is 2640 square feet.

The grate is an undivided area of 63.25 square feet, and is fired through four properly spaced doors.

BOILER DATA

Kind of boiler, Babcock & Wilcox-" Alert" type. Diameter of top drum, 42 inches, inside. Length of top drum, 12 feet. Tubes: total number, 565; length, 8 feet (525, 2 inches outside diameter, and 40, 4 inches outside diameter). Grate surface: length, 6 feet 84 inches; width, 9 feet 51⁄2 inches; area, 63.25. Grate surface reduced in tests Nos. 5 and 6, to 5 feet 6 inches; 52 square feet area. Heating surface: area, 2640 square feet; ratio to grate, 41.74:1. Per cent. water-heating surface, 100. Grate bars: kind, fixed.

above grate; ratio to grate, 1:8.03.

Smoke pipe: area, 7.876 feet; height, 48 feet Weight of boiler and all fittings except up-takes

Area of

Total weight per square foot of heating surface, pounds

Blower: kind, 60-inch Sturtevant, driven by belt from shop engines. blower inlet, 9.62 square feet; outlet, 6.89 square feet. Feed water: kind, feed water heated by steam jet. Air heater: kind, two-pass; 3-inch tubes. Area of surface, 495 square feet.

Feed pumps. kind, Worthington duplex; dimensions of cylinders, 71⁄2 by 4; 6-inch stroke. Other boiler appurtenances: steam jet.

The boiler was erected in a wooden structure built especially for the test and having the following dimensions: Length, 29 feet 2 inches; width, 17 feet 21⁄2 inches;

*Extracts from the " Journal of the American Society of Naval Engineers," Volume XII.

height, 21 feet. This was made as nearly air-tight as possible, but contained several windows that could be opened or closed to regulate the amount of draft pressure. The blower was driven by belting from the main shop engines and ran continually.

An air heater was built in the up-take by means of which the waste gases imparted heat to the air on its passage to the ash pit. This heater could be placed in and out of service at will by the use of a by-pass flue.

DESCRIPTION AND OBJECT OF TESTS

Seven tests were made in all. Six of these consisted of three pairs, in which the tests of each pair were made under similar conditions in every way except that of using the air heater, one being with and the other being without this heater, in order to define the economy due to its use. The last or seventh test was for maximum capacity, and was made without the air heater and with the full grate. Two pairs of tests, one at a consumption of about 20 pounds of coal and the other at about 35 pounds of coal per square foot of grate per hour, were made with the full grate surface in use. These tests will be found in tables of results numbered 1, 2-H, 3-H, 4, the letter H signifying that the air heater was in use during the tests. The grate surface was then reduced to 52 square feet, by a course and a half of bricks, seven courses in

height, at the back of the furnace, and tests Nos. 5 and 6-H were made, burning about 50 pounds of coal per square foot of grate per hour. The bricks were then removed from the furnace and test No. 7 was made, burning nearly 60 pounds of coal per square foot of grate per hour. The data and results of these tests will be found in the table on pages 158 and 159.

COAL AND FIRING

The fuel used was Pocahontas, Flat Top, coal. It contained considerable slate and clinkered badly. On tests Nos. 1 and 2-H run-of-mine coal was used; on tests Nos. 3-H, 4, 5 and 6-H the coal was screened, using a screen with a 1-inch mesh. On test No. 7 the screenings from the former tests were run over a 3%-inch mesh screen, and the coal thus screened was mixed with the screened coal used in other tests. The firing was good and very regular. Two alternate doors were fired in rapid succession. The other two sections of fires, in wake of the other two doors, were sliced through the slicing door, and then leveled with a hoe, and then coaled, the average time between coalings of the same two furnaces being from eight to ten minutes. The furnace doors were open about twenty-five seconds when coaling and about ten seconds in leveling. The coal made comparatively little smoke except when firing or working fires. The data in regard to smoke was taken by using Ringelmann charts.

DESCRIPTION OF APPARATUS

The water was weighed in two tanks, each supported on a platform scales and run into a third tank below, from which the feed pumps drew water. All pipes were above ground and in plain sight, and wherever connected to other piping or boilers, plugs were left out of T connections to show that there was no leakage. The gross and tare weights of each tank were taken, and the temperature was taken at the lower tank just as each upper tank drained into it. The feed water was heated by steam injection before entering the weighing tanks.

The coal was weighed in barrows on platform scales in the fire room and dumped on the floor. The time was taken when each lot of barrows were fired.

A sample shovelful of coal was taken from each lot of barrows and thrown into a barrel, and from this, mixed and quartered, the final samples for analyses, calorimeter and moisture determinations were taken. The gases for analyses were drawn from near the center of the base of smoke pipe by means of a pipe inserted therein connected with an inspirator and a small Orsat instrument.

All draft pressures were taken outside the building, pipes being led there from the different places where pressure determinations were required.

Temperatures were taken at the back and front of the up-take just above the heater; in front by a mercurial pyrometer, and at the back by a metallic pyrometer. When the air heater was used the temperature was taken in addition just below the heater by means of a mercurial pyrometer.

The moisture in the steam was determined by a Barrus universal calorimeter. The steam was found practically dry in all cases. The steam was partly used in the shop and partly blown off into the atmosphere, the pressure being controlled by regulating a small stop valve by hand.

TEMPERATURE OF GASES PASSING THROUGH BOILER AS SHOWN BY MELTING POINT OF METALS-TESTS OF "CINCINNATI" BOILER

Experiments to show the heat of the gases at various points were made by noting the points at which different metals melted. A small piece of metal was wired to a piece of 4-inch pipe, and pushed in carefully through the dust doors at the side of casing to about the middle of the boiler; by noting where such metal would melt, and again introducing a piece of the same metal at another hole further along in the path of the gases until a position was reached when the metal would not melt, and by the use of various metals with known melting points, the temperature of the gases was determined and is plotted on the diagrams on the opposite page.

Before making test No. 6-H, on June 21st, all water was drained from the boiler and the contents of boiler noted for each 1-inch mark of the water gauge glass, with the following results :

WEIGHT OF WATER CONTAINED IN BOILER

Fires were started in the boilers with light wood, and blower in use, at 9:40 A. M. Temperature of water in boiler, 72 degrees; height in gauge glass, 1 inch.

The following is a record of the time required to raise steam to 215 pounds pressure from cold water:

An examination of the boiler after this test showed no injury or change in its condition in any respect.

In addition to the tests made for the Navy Department, three tests were made for The Babcock & Wilcox Company by E. H. Peabody, Mem. Am. Soc. M. E. The data and results of these tests are included with the others in the following table: